A number of observations support the concept of important physiological interactions between the endocrine and immune systems. It could be confirmed that hormones secreted by the neuroendocrine system play an important role in communication and regulation of the cells of the immune system. Among protein hormones, this has been most clearly documented for prolactin (PRL), growth hormone (GH), and insulin-like growth factor 1 (IGF-1). A number of traits of the immune response in a Duroc x Berlin Miniature pig family (DUMI) were examined. The haemolytic complement activity in the classical complement pathway (CH50) and the alternative pathway (AH50)was examined at eight different time points in pigs that were vaccinated with different vaccines. Single nucleotide polymorphism (SNP) genotyping was employed to genotype the DUMI F2 animal for growth hormone (Gh), growth hormone releasing hormone (Ghrh), pituitary-specific transcription factor 1 (Pit1), and prolactin receptor (Prlr) loci, and also a microsatellite within insulin-like growth factor 1 (Igf1). Using a family-based association test (FBAT) program, a highly significant association of Gh, Pit1, and Prlr to AH50 (p < or = 0.01) and a significant association of Pit1 to CH50 (p < or = 0.05) were found. Using the SAS system for mixed model, a highly significant association of Gh, and Igf1 to AH50 and CH50 (p < or = 0.01) was detected, while Prlr and Ghrh had a highly significant association (p < or = 0.01) with CH50 only.